These chips were low performance and limited number of write cycles. Even with a great controller (which would be expensive) you're looking at slow transfer rates. If it reaches USB 2 capabilities, you're lucky. This guy kinda was.
UFS/eUFS cards keep (sort of) same form-factor [1] but bring significant speed boost. [2]
[0] Technically, it is incorrect to say "eMMC chip", as there are typically two (or more) silicon chips inside the same plastic BGA package. One of them is controller.
[1] https://www.dpreview.com/news/6387181333/samsung-launches-fi...
[2] https://en.wikipedia.org/wiki/Universal_Flash_Storage#Versio...